Research On Integrated Nano-vacuum Electron Source Based On Microfluidic Heat Dissipation

Electron source is one of the core components of microwave electric vacuum device.The development of information technology makes electronic devices continue to develop in the direction of high frequency,miniaturization and integrated applications.Affected by the size co-transition effect,the size of microwave vacuum devices increases with the increase of frequency,and the required current density increases,while the size becomes smaller and smaller.Traditional hot cathodes have been difficult to meet the needs of high-frequency terahertz devices.Cold cathodes have the characteristics of no heating,small size,and high current density,and are ideal electron sources for millimeterwave and terahertz devices.However,due to the uneven emission of the cold cathode,the heat accumulation at the local emission tip is serious.Under extreme conditions,the local heat flux density of the cold cathode can exceed 10 k W/cm2,far exceeding the thermal conductivity of the cathode material.Therefore,the emission stability and reliability of the current cold cathode are poor,which becomes the bottleneck of its application.Microfluidic heat dissipation is to prepare micron-scale flow channels inside the substrate of electronic devices,so that the device can obtain great heat dissipation capacity.Studies have shown that its peak heat dissipation capacity can reach 30 k W/cm2,which is an effective method to improve the heat dissipation of high-power devices.In this thesis,through the combination of simulation and experiment,the multiphysics coupling simulation and collaborative design of microfluidic heat dissipation is carried out on the field emission cold cathode substrate,and it is combined with the field emission electron source to conduct experiments to study the effect of heat dissipation on the cathode emission performance.The main research contents include:Research on multiphysics coupling simulation collaborative design of microfluidic heat dissipation substrate.Use COMSOL Multiphysics simulation software to simulate the heat dissipation model of the substrate,and simulate the influence of different structures and parameters on the heat dissipation of microfluids,including: fluid flow characteristics,heat transfer area,flow velocity and other fluid simulations;channel depth,heat transfer area and Structure simulation of fluid velocity,etc.;and comprehensive simulation design of fluid laminar flow,turbulent flow structure,channel pressure drop,channel inlet structure,etc.Preparation,analysis and testing of microfluidic heat dissipation substrates.According to the simulation results,the heat dissipation substrate is processed,and the metal thin film resistor is deposited by magnetron sputtering as the heat source.Considering the need to combine with the vacuum chamber when building the heat dissipation test platform,design a specific water inlet and outlet structure and complete the assembly of the heat dissipation substrate.Finally,the heat dissipation capacity test is completed,and the cause of the error is analyzed.Preparation and performance testing of microfluidic bulk cold cathodes.Explore the cathode fabrication process,including the selection of emissive materials,slurry ratio,annealing temperature,etc.In this thesis,two structures of on-chip electron sources were designed,and the morphologies were characterized after fabrication.Finally,the emission performance under different conditions is tested.The results show that the planar nanovacuum electron source has poor emission performance due to the imperfect processing process,while the vertical nano-vacuum electron source has good emission performance.The heat dissipation test results show that the microfluidic heat dissipation substrate has a certain improvement in the performance of the electron source.